Bias field effect on the temperature anomalies of dielectric permittivity in PbMg1/3Nb2/3O3- PbTiO3 single crystals

TL;DR

This study investigates how bias electric fields influence the temperature at which dielectric permittivity peaks in certain relaxor ferroelectric crystals, revealing complex phase behaviors and the effects of quenched random fields.

Contribution

It provides new insights into the bias field dependence of phase transitions and phase diagram construction in PbMg1/3Nb2/3O3-PbTiO3 single crystals, highlighting the interplay of relaxor, ferroelectric, and glass phases.

Findings

The temperature of permittivity maximum can decrease or stay constant with bias field up to a threshold.

Constructed T-E phase diagrams showing relaxor, ferroelectric, glass, and mixed phases.

Identified a first-order phase transition boundary with thermal hysteresis and an end-point in the phase diagram.

Abstract

In contrast to ordinary ferroelectrics where the temperature, Tm, of the permittivity maximum monotonically increases with bias field, E, in (1-x)PbMg1/3Nb2/3O3-(x)PbTiO3 (0<x<0.35) single crystals, Tm was found to remain constant or decrease with E up to a certain threshold field, Et, above which Tm starts increasing. Et decreases with x and almost disappears at about x=0.4. We explain this field dependence by the quenched random fields and coupling between the orientable dipoles with average polarization. For crystals with 0.06<x<0.13, the T-E phase diagrams are constructed, which include the relaxor, ferroelectric, glass and mixed ferroelectric-glass phases. The boundary between the ferroelectric and relaxor phases corresponds to a first-order phase transition and is characterized by thermal hysteresis with a large curvature of the line obtained in the field cooling mode, and by the presence of the end-point above which there is no difference between the ferroelectric and relaxor phases. The glass phase has a nearly field-independent boundary in the vicinity of the Vogel-Fulcher temperature TVF. The coupling between the glass order parameter and polarization changes the ferroelectric boundary at temperatures lower than TV